“Urea to Urea” Approach: Access to Unsymmetrical Ureas Bearing Pyridyl Substituents
作者:Svetlana O. Kasatkina、Kirill K. Geyl、Sergey V. Baykov、Mikhail S. Novikov、Vadim P. Boyarskiy
DOI:10.1002/adsc.202101490
日期:2022.3.30
A protocol for the synthesis of unsymmetrical ureas substituted by pyridyl/quinolinyl moiety has been developed. This method concluded in metal- and base-free reamination of N,N-dimethyl-N‘-hetaryl ureas with a wide range of aryl and alkyl amines. The isolated yields vary from 40 to 96% depending on the nucleophilicity of the amines. The scope of this method includes more than 50 examples. The reaction
The conversion of 1,3-bis-(6-amino-pyridin-2yl)-urea (1) with N',N'-carbonyldiimidazole at high temperatures in DMSO yielded a mixture of defined cyclic trimers and tetramers. On the basis of model reactions, exchange reactions were evidenced, which convert the cyclic tetramer into a stable cyclic trimer. Linear even numbered oligomers were obtained in acetone under reflux where side reactions were suppressed. The pronounced tendency of cyclization is attributed to a preferred folded conformation of the urea bond between two pyridyl units.